It is known to provide an applicator which has a spool of the tape, defined as the support strip and the adhesive film detachably adherent thereto, and a take-up spool or means on a structure which is swingable out of the housing to allow access to the spools.
In conventional devices of this type, as in a sound-recording cassette, the supply spool and the take-up device are provided in a common plane and the supply spool carries a multiplicity of turns of the support strip coated with the adhesive film such that the adhesive film tends to adhere to the substrate with a greater force than it is adherent to the support strip, whereby upon movement of the applicator over the substrate or movement of the substrate, which can be paper, past the applicator, the tape is moved through a corresponding distance and the adhesive film from this tape is transferred to the substrate.
The take-up device can be analogized to the take-up spool of a sound-recording cassette. The take-up device and the supply spool can be mounted on a structure adapted to be swung out of a housing to allow replacement of the supply spool when the latter is empty and removal of the coil of the strip from which the adhesive film has been detached.
On the outer side of the housing, and indeed on a small side thereof, the transfer device is provided.
The film-coated strip, i.e. the transfer tape, is directed out of the housing and has its nonadhesive surface engaged by or passing over the transfer unit so that the opposite or obverse side of the tape, upon which the adhesive film is provided can be brought into contact with the substrate.
As a rule, the applicator is moved by hand over the substrate and the adhesive film is thereby separated from the tape, the depleted strip being wound up in a coil on the take-up device.
To facilitate the take-up of the depleted strip, a transmission can be provided between the supply spool and the take-up device to ensure that the tape will remain under tension between the take-up device and the supply spool while passing around the transfer device. In general, the transfer device has comprised a bar or roller around which the tape was stretched.
To maintain the tension with the aforementioned transmission, a slip clutch is provided in the transmission so that the transmission can ensure, as in a sound-recording cassette, that the take-up device will be driven at a speed, under all operating conditions, which is sufficient to maintain the tape under tension, around the transfer member. In practice, the transmission has utilized a belt or spiral spring loop which form the slip clutch or provided self-slip in the transmission with the effect of a slip clutch or a gear drive in conjunction with a separate slip clutch.
When in the application of the adhesive film to a substrate, the device was canted or when the substrate was not absolutely even or could not be placed in a planar orientation so that the applicator could contact the substrate only along one side of the application, there was an uncontrolled tearing of the adhesive film. This resulted not only in the application of an unsatisfactory adhesive film trace to the substrate, but also could prevent the advance of the tape and thus the take-up of the depleted strip. The further application could result in the emplacement of only a torn film or an interruption in operation by contamination of the applicator itself with pieces of the adhesive film and possibly even bunching or jamming of the tape so that a significant effort was required to clear and clean the applicator.
In an effort to reduce the effect of this drawback, it has been proposed to broaden the transfer device with portions of either side of the applicator film intended to come into contact with the substrate. In this case, upon a canting of the applicator with respect to the substrate for any reason, the adhesive film does not come into partial contact with the substrate and hence is not torn. Furthermore, the breadth of the transfer device can be such that it is practically impossible to maintain the applicator in a tilted orientation with respect to the substrate through inadvertence.
After a completed transfer of the adhesive film, the device is usually lifted from the substrate and, as a result, the user generally does not have any control of the angle with which the film bridge between the substrate and the tape extends. Best results are obtained when this angle is a right angle since then there is the best possibility of a tear of the adhesive film in a straight transverse line. In practice, however, the inability to ensure a right angle between the edges of the applied film and the film stretch which arises from lifting results in an accordian-pleated or corrugated terminal portion of the film with the further disadvantage that the starting edge for the application of the next trace may also be irregular.
Where the tear involves sharp points in the film, these tend to be pulled back in a spring-like manner and as a result can produce a film thickness many times greater than the applied film thickness which is desired. Indeed, when the adhesive film of the invention is used to attach other objects to the substrate, the bumps resulting from the imprecise separation of the adhesive film may be visible through an article which is mounted on the substrate.
It has been proposed further to avoid the latter disadvantage by providing a brake on the device which can be actuated by hand to restrain the supply of the transfer tape and thus permit a more precise rupture of the film.
The actuation of such a brake, however, requires a higher degree of coordination of the user since the user must then coordinate a variety of movements and this, for ergonomical reasons, may be undesirable because the applicator must then be capable of accommodation to different hand sizes and different use positions.
In the use of such an applicator, moreover, certain boundary conditions play a role, these boundary conditions limiting the major dimensions of the device. The most critical dimensions are, of course, the height and length of the applicator in its direction of movement since these dimensions determine the utility of the device in applying the film to the inner surface of a vessel, a box or chest or the like.
These major dimensions, in turn, limit the size of the spool which can be used since the spool must be sufficiently small that it can be accommodated in the housing. Naturally, a small spool requires that the device be refilled more often and may make the applicator uneconomical to use because of its labor-intensive nature.
It is frequently also desirable that the device have accommodation for a reserve spool of the film-coated tape. This is problematical with conventional devices with axes for the supply spool and the take-up core which are parallel to the horizontal. Indeed in such systems, there is no possibility of an accommodation for reserve spools. If one wishes to provide a reserve spool, an additional structure must be provided on the outside of the housing and this additional compartment which projects laterally of the housing is always susceptible to damage.
Finally it has been considered to be desirable to provide a device which will enable one to readily ascertain the type of tape which is loaded in the applicator from the exterior and hence the nature of the film, e.g. its color, and to determine the quantity of the tape which remains on the spool.
As we have already noted, once the tape is fully used, the coil on the take-up device is removed and the empty supply spool is replaced by a full supply spool.
Conventional applicators have the disadvantage that the replacement manipulations must be effected within the housing of the device since the spools and the drive mechanism in the interior of the housing are integrated and therefore not readily accessible. The fingers must be inserted into the housing and frequently much of the spool replacement and emptying can only be done by finger feel. The proper positioning of the tape in the transfer device and the guide passages, the fastening of the tape on the take-up device and even the positioning of the new supply spool may require considerable time and skill, especially where there is little space for such manipulations in the housing.
Of course, if the supply spool is inserted incorrectly, i.e. in an inverted manner, it must be removed and replaced and there is always the danger that the adhesive film will contaminate parts which are never intended to contact the film.
Excessive manipulation and possibly erroneous positioning of the tape and the spool and excessive handling of the take-up coil can result in the deposition of particles of the adhesive in the body of the apparatus and even the contamination of the gear teeth or the drive so that the slip clutch may become ineffective or may shift its operating point in some detrimental fashion.
Furthermore, in conventional devices there was always the danger that an incorrect spool with an adhesive film which was not proper for a particular application could be inserted and as a result damage the device or interfere with an effective operation of it. Of course the film which might then be applied may not correspond to the wishes of the user.